1 . Field of the Invention
The present invention relates to new cure accelerators for anaerobic curable compositions. The compositions are particularly useful as adhesives and sealants.
2. Brief Description of Related Technology
Anaerobic adhesive compositions generally are well-known. See e.g., R. D. Rich, xe2x80x9cAnaerobic Adhesivesxe2x80x9d in Handbook of Adhesive Technology, 29, 467-79, A. Pizzi and K. L. Mittal, eds., Marcel Dekker, Inc., New York (1994), and references cited therein. Their uses are legion and new applications continue to be developed.
Conventional anaerobic adhesives ordinarily include a free-radically polymerizable acrylate ester monomer, together with a peroxy initiator and an inhibitor component. Oftentimes, such anaerobic adhesive compositions also contain accelerator components to increase the speed with which the composition cures.
Desirable anaerobic cure-inducing compositions to induce and accelerate cure may include saccharin, toluidines, such as N,N-diethyl-p-toluidine (xe2x80x9cDE-p-Txe2x80x9d) and N,N-dimethyl-o-toluidine (xe2x80x9cDM-o-Txe2x80x9d), acetyl phenylhydrazine (xe2x80x9cAPHxe2x80x9d), maleic acid, and quinones, such as naphthaquinone and anthraquinone. See e.g., Loctite U.S. Pat. No. 3,218,305 (Krieble), U.S. Pat. No. 4,180,640 (Melody), U.S. Pat. No. 4,287,330 (Rich) and U.S. Pat. No. 4,321,349 (Rich).
Saccharin and acetylphenyl hydrazine (xe2x80x9cAPHxe2x80x9d) have been used as standard cure accelerator components in anaerobic adhesive cure systems since the inception of the technology. Loctite currently uses either saccharin alone or both saccharin and APH in most of its anaerobic adhesives.
Other curatives for anaerobic adhesives include thiocaprolactam (e.g., U.S. Pat. No. 5,411,988) and thioureas [e.g., U.S. Pat. No. 3,970,505 (Hauser) (tetramethyl thiourea), German Patent Document Nos. DE 1 817 989 (alkyl thioureas and N,Nxe2x80x2-dicyclohexyl thiourea) and 2 806 701 (ethylene thiourea), and Japanese Patent Document No. JP 07-308,757 (acyl, alkyl, alkylidene, alkylene and alkyl thioureas)], certain of the latter of which had been used commercially up until about twenty years ago.
Recently, Loctite Corporation has discovered a new class of materialsxe2x80x94trithiadiaza pentalenesxe2x80x94effective as curatives for anaerobic adhesive compositions. The addition of these materials into anaerobic adhesives as a replacement for conventional curatives (such as APH) surprisingly provides at least comparable cure speeds and physical properties for the reaction products formed therefrom. (See International Patent Publication No. WO00/40664.)
In a UV curable anaerobic adhesive system, ThreeBond Co. Ltd. appears to have disclosed the use of the combination of 1-(2-carboxyacryloyl)-2-phenylhydrazine and o-benzoic sulfimide. See Japanese Patent Document No. JP 05-105,847.
Nonetheless, there is an on-going desire to find alternative technologies for anaerobic cure accelerators to differentiate existing products and provide supply assurances in the event of shortages or cessation of supply of raw materials. Accordingly, it would be desirable to identify new materials which function as accelerators in the cure of anaerobic curable compositions.
The present invention provides new cure accelerators for anaerobic curable compositions. The cure accelerators include the xe2x80x94C(xe2x95x90O)xe2x80x94NHxe2x80x94NHxe2x80x94 linkage, together with an organic acid functional group on the same molecule. For instance, the inventive cure accelerators may be within structures I or II 
where R1, R2 and R3 in structure I and R1, R2, R3, R4, R5, R6 and R7 in structure II are each independently selected from hydrogen or C1-4; Z is a carbon-carbon single bond or carbon-carbon double bond; q is 0 or 1; and p is an integer between 1 and 5.
The addition of these materials into anaerobic curable compositions as a replacement for some or all of the amount of conventional anaerobic cure accelerators (such as APH or the toluidines noted above) surprisingly provides at least comparable cure speeds and physical properties for the reaction products formed therefrom. It is desirable that the anaerobic cure accelerators excludes 1-(2-carboxyacryloyl)-2-phenylhydrazine. It is alternatively or additionally desirable that the composition is not rendered UV curable by the addition of a UV photoinitiator.
This invention also provides anaerobic curable compositions prepared with such cure accelerators, methods of preparing and using the inventive anaerobic cure accelerators as well as reaction products of the inventive anaerobic curable compositions.
The present invention will be more fully appreciated by a reading of the xe2x80x9cDetailed Description of the Inventionxe2x80x9d, and the illustrative examples which follow thereafter.